High-tech computerized off-gas combustion treatment and apparatus

ABSTRACT

An exhaust system adapted for the selective control of the types and concentrations of emissions to the atmosphere in the off-gas of a combustion unit, the system including at least one chemical treatment chamber, at least one off-gas, kinetic energy reducing chamber communicating with at least one chemical treatment chamber and adapted to provide a reduced pressure off-gas region wherein the kinetic energy of the off-gas from the treatment chamber is diminished, at least one chemical reactor communicating with at least one treatment chamber and adapted to provide reactant chemicals in contact with the off-gas in the treatment chamber, at least one reactant chemical selecting system associated with at least one chemical reactor and adapted for presenting different chemicals and concentrations thereof to the off-gas in at least one treatment chamber, cooling apparatus for the off-gas in one or more selected portions of the exhaust system, and a control system communicating with the off-gas at one or more locations within the exhaust system for qualitatively and quantitatively analyzing the off-gas and actuating the selecting system in relationship to the gas analysis to provide selected reactant chemicals in predetermined quantities to at least one chemical reactor for contact with the off-gas to selectively control the types and concentrations of matter therein.

FIELD OF INVENTION

This invention concerns method and apparatus for the handling ofcombustion off-gas or flue gas, and particularly concerns such methodand apparatus which are readily adapted to existing incineration,heating or power installations, and which effect improved control of thetypes and amounts of gaseous, ionic, colloidal or sizeable particulateoff-gas constituents such as fly ash which are ultimately vented to theatmosphere. Also, the method and apparatus are uniquely adapted toemploy the kinetic energy of the off gas and steam-developed backpressure to generate power through turbine equipment or the like.

BACKGROUND OF INVENTION AND PRIOR ART

The air pollution problems associated with such combustion by-productsas, for example, the various oxides of nitrogen, sulfur, carbon,phosphorus, mercury and other metals, the various halides such as HCland HBr, the phosphoryl compounds, the many other volatile metalhalides, oxides and complexes, the various sulfur containing compoundssuch as hydrogen sulfide or carbon disulfide, and the organic toxicpollutants such as dioxin and the like which are strongly adsorbed onfly ash, are well recognized and of course, are the subject of enormousinternational research and development effort. Such by-productstypically are produced through garbage or trash incineration, orbuilding heating, power production or the like from fossil or otherfuels.

Industry has responded to these problems with many pollution controldevices and processes such as off-gas scrubbing, filtering, electricalprecipitation, electric arc afterburning, catalytic burning, baffledflues and chimneys, and the like, many of which are of limited practicalvalve, particularly for the effective removal of fly ash and otherparticulate fines, and practically all of which require large andexpensive special auxilliary off-gas handling equipment and housingstructures therefor. Ofttimes these control devices are not adaptable toexisting flue equipment and the cooperating or supporting equipment orinstallations comprises several buildings or at least severalinterconnected but separate installations of scrubbers, cycloneseparators, filter equipment, economizers, and the like, whichnecessarily complicate the off-gas treatment aspect, both labor andapparatus, particularly maintenance, and leads to unmanageable cost ofoff-gas clean up. Typical such prior installations are depicted anddiscussed in the Allen Hershkowitz article in Technology Review, July30, 1987, and in U.S. Pat. Nos. 3,710,555; 3,706,182; 3,695,004;3,984,220; 4,095,514; 4,286,973; 4,206,722; 4,635,569; and 3,442,232,the disclosures of all of which are incorporated herein by reference,particularly the relevant structures thereof, e.g., the spray or jetnozzles.

Objects of the present invention therefore, are:

(1) to provide an off-gas treatment process and apparatus therefor whichis useable as original equipment or readily adaptable to existing fluestructures at minimum reconstruction effort and cost, and which ishighly effective in reducing the levels of undesirable air pollutants,especially particulate fines;

(2) to provide such process and apparatus which is provided withscrubbing means adaptable to automatic, electronic control;

(3) to provide such process and apparatus with continous orsemi-continuous off-gas monitoring analysis, computer interpretation ofthe analysis data and computer regulation of chemical reactor meanswithin the flue system for reacting out normally pollutant chemicals inresponse to said computer interpretation; and

(4) to provide such method and process which is energy efficient andcapable of effectively generating power, particularly electric power.

SUMMARY OF THE INVENTION

These and other objects hereinafter becoming evident have been attainedin accordance with the present invention which, in its processembodiment is defined as the process for selectively controlling theconcentration of one or more constituents in the off-gas of a combustionunit having a fire box and a flue system, comprising carrying out thefollowing activities, in any order, in a continuous or semi-continuousmanner;

(a) analyzing the chemical composition of the off-gas at one or morelocations in said flue system;

(b) directing the off-gas from the fire box into chemical treatmentchamber means maintained at predesigned off-gas pressures;

(c) contacting the off-gas in said treatment chamber means with reactantchemical means previously adjusted in reactivity and specificityaccording to the chemical analysis of the off-gas, for convertingprescribed amounts of one or more of the constituents of said off-gas toone or more desired products;

(d) exiting the treated off-gas from said treatment chamber means tosecond chamber means maintained at predesigned off-gas pressures lowerthan the off-gas pressures maintained in said treatment chamber means toeffect a reduction in the kinetic energy of the treated off-gas and thusfacilitate removal of particulate matter therefrom; and

(e) exiting the reduced kinetic energy off-gas from said second chambermeans to the atmosphere or other desired medium or apparatus.

In certain preferred process embodiments:

(1) the reduced kinetic energy off-gas is passed through filtering meansfor removing particulate matter therefrom prior to exiting to theatmosphere;

(2) said off-gas in said second chamber means is scrubbed with aqueousmaterial to separate particulate matter therefrom;

(3) the temperature and kinetic energy of the off-gas in the treatmentchamber means is further reduced by contact of the off-gas with heatexchanger cooling means;

(4) said reactant chemical means comprises aqueous material containingat least one reactant chemical and is injected as a spray into saidoff-gas; and

(5) the off-gas and steam from the second chamber means is directed topower generating apparatus.

The apparatus embodiments of the invention is defined as an exhaustsystem adapted for the selective control of the types and concentrationsof gaseous, ionic, collodial or particulate matter emitted to theatmosphere in the off-gas of a combustion unit, said system comprising:

(a) chemical treatment chamber means defined by

(i) first wall means,

(ii) off-gas inlet means in said first wall means, and

(iii) outlet means in said first wall means providing an exit forchemically treated off-gas from said treatment chamber means;

(b) second wall means defining off-gas, second chamber meanscommunicating with said outlet means of said treatment chamber means andadapted to provide a reduced pressure off-gas region;

(c) exhaust port means in said second wall means for exiting reducedkinetic energy off-gas;

(d) reactor means communicating with said treatment chamber means andadapted to provide reactant chemicals in contact with the off-gas insaid treatment chamber means;

(e) reactant chemical selecting means associated with said reactor meansand adapted for presenting different chemicals and concentrationsthereof to said off-gas in said treatment chamber means;

(f) cooling means for the off-gas in one or more selected portions ofsaid exhaust system; and

(g) control means communicating with the off-gas at one or morelocations within said exhaust system for qualitatively andquantitatively analyzing the same and actuating said selecting means inrelationship to said analysis to provide selected reactant chemicals inpredetermined quantities to said reactor means for contact with saidoff-gas to selectively control the types and concentrations of saidmatter therein.

In certain preferred apparatus embodiments:

(1) third wall means provides exhaust stack means communicating withsaid exhaust port means of said second chamber means;

(2) said first, second and third wall means are interconnected;

(3) said treatment chamber means is elongated and adapted forpositioning above and in communication with the fire box of a combustionunit with its longitudinal axis oriented substantially vertically;

(4) said control means provides substantially continuous off-gasanalysis and reactant chemical selection;

(5) said reactor means comprises multiple fluid streams of differentchemical compositions;

(6) cooling means is provided for maintaining said second chamber meansat a reduced temperature;

(7) said second chamber means is positioned substantially verticallyabove said treatment chamber means;

(8) common cooling means is provided for said reactor means and secondchamber means; and

(9) said common cooling means comprises heat exchanger means within saidsecond chamber means or proximate thereto.

The invention will be further understood from the following descriptionand drawings wherein:

FIG. 1 is a longitudinal sectional view of an off-gas exhaust systemembodying the present invention as installed directly onto the off-gasoutlet of a fire-box;

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1 in thedirection of the arrows;

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1 in thedirection of the arrows;

FIG. 4 is a longitudinal sectional view of a variation of the apparatusarrangement;

FIG. 5 is a transverse, cross-sectional view of the chemical treatmentsection of the exhaust system of FIG. 4 showing a variation of thechemical reactor means;

FIG. 6 is a varation of the power generating area of the system; and

FIG. 7 is a schematic of an overall computer system for operating thevarious components of the apparatus.

BRIEF DESCRIPTION OF THE INVENTION

A brief description of the present invention, with reference to thedrawings and claims hereof comprises:

(a) chemical treatment chamber means 10 defined by

(i) first wall means 12,

(ii) off-gas inlet means 14 in said first wall means, and

(iii) outlet means 16 in said first wall means providing an exit forchemically treated off-gas from said treatment chamber means;

(b) second wall means 18 defining off-gas second chamber means 20communicating with said outlet means 16 of said treatment chamber meansand adapted to provide a reduced pressure off-gas region;

(c) exhaust port means 22 in said second wall means for exiting reducingkinetic energy off-gas;

(d) reactor means 24 communicating with said treatment chamber means andadapted to provide reactant chemicals in contact with the off-gas insaid treatment chamber means;

(e) reactant chemical selecting means 26 associated with said reactormeans and adapted for presenting different chemicals and concentrationsthereof to said off-gas in said treatment chamber means;

(f) cooling means 28 for the off-gas in one or more selected portions ofsaid exhaust system; and

(g) control means 30 communicating with the off-gas at one or morelocations within said exhaust system for qualitatively andquantitatively analyzing the same and actuating said selecting means inrelationship to said analysis to provide selected reactant chemicals inpredetermined quantities to said reactor means for contact with saidoff-gas to selectively control the types and concentrations of saidmatter therein.

It is seen from the above description and gas flow path arrows in FIG.1, that outlet means 16 from the chemical treatment or initial scrubbingsection of the exhaust system presents a gas flow exit across which apressure drop occurs, either as the result of the exit being restricted,or of cooling of the second chamber, or both, and effects gas expansionand/or a cooling, and reduction in kinetic energy of the off-gas. Thisdiminishment of molecular and ash particle activity enhances theseparability of pollutant materials from the off-gas and controls backpressure on the overall exhaust system which, if excessive, would reduceits capacity and efficiency.

DETAILED DESCRIPTION

Referring further to the drawings, the exhaust system is shown as aconcentrically multicylindered, columnar stack generally designated 32fitted over the outlet neck 34 of a combustion chamber or firebox 36,the stack preferably being oriented in practise essentially vertically.Such a stack is readily assemblable, without significant alteration ofexisting auxillary or supporting structure, onto many fireboxespresently in use in incinerator or power installations, in that it issubstantially self contained and handleable as a single unit. In thisregard, the stack 32 can be dimensioned in cross-section and length toaccommodate existing equipment in virtually any installation. It isnoted that the present exhaust system does not have to be affixeddirectly to a firebox outlet, but is insertable into the existing flueworks of an incineration system at any desired location. In this regard,36 as shown may be a clean-out or utlility chamber and the off-gassesmay be received through a flue 37 connected to a combustion chamber at alocation removed or remote from chamber 36.

The reactor means 24 is shown as a series of fluid jets of anyconvenient number mounted in wall 12 in any desired locations andconnected by suitable piping or conduit 38 to chemical selecting means26 which is provided with suitable valving such as solenoid flow-controlvalves 40, 42, 44 and 46 communicating respectively with the chemicalfeed reservoirs 48, 50, 52 and 54 which are typically pressurized insome manner to effect the proper flow of the chemical reactants. Anynumber of solenoid or equivalent valving can be employed in conjunctionwith any number of chemical reservoirs. Also, more complex flow-controlvalving may be employed to premix the various chemicals, if such isdesired, according to what reactions are required to control off-gaspollutants.

In the embodiment shown, the jet feed conduit 38 is positioned onopposite sides of wall 12 in chamber 10 and is continuous at the bottomby half encircling wall 12. Several such feed conduits may be positionedaround the reaction chamber. Conduit 38 extends upwardly and isconnected into a mixing ring 39 to which the four chemical feed conduits40, 42, 44 and 46 are fluid connected. It is noted that in a preferredembodiment of the invention, the various chemicals received from theaforesaid reservoirs are cooled in chamber 62 and intimately mixedwithin ring 39 prior to descending to the reactor jets. As a supplementto the jets in chamber 10, additional jets 55 may be provided on conduit38 within the expansion chamber to further facilitate any necessaryreactions. These additional jets, may however, be connected to anotherpiping system, preferably cooled, to deliver scrubbing water rather thanchemical reactants.

The control means generally designated 30 comprises one or moregas-analyzer probes or samplers such as 56 strategically placed withinthe exhaust system, preferably at the inlet to the reaction chamber 10,within the second chamber 20, and in the final exhaust chimney 72, andoff-gas analysis means 58 which is electronically associated withcomputer means 59 through electrical conduit 60, computer means 59 beingprovided with programmable capability for interpreting the off-gasanalysis data with respect to the chemical feeds necessary forconverting the primal off-gas constituents to the types and levelsdesired or tolerable in atmospheric emissions. The output signals of thecontrol means 30 are transmitted, e.g., through electrical conduit 61 tothe flow-control solenoid valves of the chemical selecting means 26 toadjust the type and amount of reactant chemical feed to the ejectors orother reactor means.

The reactant chemical compositions which may be employed in practisingthe present invention are practically unlimited in variety, and a largenumber are well known and utilized for the control of elemental and thevarious compounds of mercury, lead, cadmium, sulfur, nitrogen, halogen,carbon, phosphorus and the like, as well as larger organic moleculessuch as dioxin, aldehydes, ketones, noxious sulfur containing organicmolecules such as mercaptans, and the like. Examples of such chemicalreactants are given in U.S. Pat. Nos. 3,728,433; 3,728,441; 3,728,440;and in T909,017, the disclosures of all of which are incorporated hereinby reference.

The various useful reactant chemicals typically employed in off-gasscrubbing operations include water per se, aqueous slurries of CaCO₃,CaO, NH₃, and other such basic materials including NaOH and KOH, metalchelators such as ethylenediametetraacetic acid, ferrous iron compounds,cyanuric acid, yellow phosphorus aqueous emulsion, alkylamines, sulfamicacid, KMnO₄, HNO₃, and aqueous hypochlorite. The particular chemicalemployed, i.e., selected in accordance with the present invention inresponse to the analysis data from control means 30, will be determinedby the off-gas composition at the analysis sampling sites in the exhaustsystem and the desired or targeted emission composition to theatmosphere.

The type of off-gas analysis device useful in the present invention may,of course, be widely varied, and dependent to some degree on theprincipal types of combustible material to be fed to the firebox orcombustion chamber. Typical useful gas sampling and analysis systems,both quantitative and qualitative, are disclosed in: the sales brochuresof Enmet Corporation, Ann Arbor, Mich., and in the sales brochures ofGastech Corporation, Newark, Calif.; and in the Product Line Catalog ofTHERMO ENVIRONMENTAL INSTRUMENTS INC., Franklin, Mass., pages 1-45,especially pages 27-31 wherein is shown and described a Flue GasAnalyzer System particularly adapted for use in the present invention.Various computerized systems for recording and interpreting theanalytical data, and for actuating the valving means for pumping therequired chemical solutions or slurries to the injector nozzles areknown to the art of computers and related servosystems.

The cooling means is shown as the conduit 28 which is connected to afluid coolant source such as the cooling coils of a refrigeration unit,or a circulating cooling water source. The coolant fluid is preferablymaintained below about 40 F. Conduit 28 is coiled around mixing ring 39which is preferably mounted in a coolant chamber 62 formed by the upperside wall portion of wall 18, top 64 thereof, and floor 66. Any numberof such rings 39 and cooling coils may be employed. Also, ring 39 may bein the form of a grid such that each chemical feed will travel atortuous path for more intimate reactant mixing and enhanced coolingthereof. Alternatively or supplemental to conduit 28, this chamber 62may be hermetically sealed and provided, in a continuing manner, withliquid coolant, such as the expanding or expanded refrigerant gas of arefrigeration unit, chilled water, or the like, through suitable fluidconduit means.

The capacity of the cooling means 28 and any supplemental system, inconcert with the degree of expansion of the off-gas across exit 16, ifsuch restricted exit is employed, should be such that the ratio of theaverage gas pressures in chamber 20 to the average gas pressure inchamber 10 preferably is between about 0.95 to about 0.75, and mostpreferably from about 0.9 to about 0.8, although any pressure drop inchamber 20 will effect some salutary diminution in the escape propensityof particulate material such as to enhance its capture by, e.g., aqueousscrubbing. The pressure in chamber 20 is a function of chamber coolanttemperature, the mass and kinetic energy of incoming gasses, steamcondensation rate, exhaust system temperature, and the like parameters.In preferred embodiments, such parameters are monitored by suitablemeasuring devices, i.e., thermostats, humidistats, or the like, andregulated to maintain adequate pressure in chamber 20 to operate powergenerating equipment such as gas turbine, electrical generators 94. Suchparameter monitoring devices can be placed anywhere in the exhaustsystem and associated with a computer network such that, e.g., thetemperature of the reactant materials and or the coolant in chamber 62,or even the rate at which combustibles are fed to the firebox, can beautomatically regulated to maintain adequate pressure of the turbine gasfeed. Where the cooling means utilizes the cooling fluid of arefrigeration unit, the reactant chemical feed conduits may bepositioned adjacent thereto for convenient cooling of the chemicalfeeds. Such chemical cooling, preferably below about 40 F, reduces thekinetic energy of the off-gas in chamber 10 and assists in stabilizingdesired reaction products formed therein.

In order to maximize the removal of pollutant fly ash and otherparticulate matter, structure is provided to cause the chemicallytreated, scrubbed and expanded off-gas and resultant slurry andcondensation to follow a baffled path for further particle sizereduction and filtering. This structure comprises grid channel 68,downcomers 70, and exhaust chimney 72 formed by wall means 69, 71 and18. Channel 68 preferably is provided along its entire length andcircumference with stainless steel baffle projections 74 of such shapeas to break fly ash particles within the aqueous slurry into smallerpieces for easy transport through disposal conduit means such as shownas 75. This channel, containing cooled slurry, will act as a thermalbarrier to the initial off-gas heat in chamber 10. In order to directthe slurry into this channel, an angled splash plate 76 is providedencircling the channel perimeter. The lower end of channel 68 may beprovided with a chemical treatment section 78 filled with limestonechunks, or other chemically reactive material, to convert the slurrypassing through grid separators 80 to, for example, a neutral pH aqueoussystem. Suitable drain lines such as 82 and clean-out access doors 84may be provided for this section.

The gaseous material from second chamber 20 may be further treated indowncomers 70. Each port means 22 may be provided with a cap or grid ofany shape and structure to minimize the flow of slurry therethrough intothe downcomers. Filtering means of any composition and construction,including granular material, may be provided in the downcomers which areprovided with access doors such as 88. The filter means may be ofelongated, self-supporting material such as stainless steel wool type,in the form of a cartridge for easy insertion up into the downcomers andfor easy removal therefrom when depleted or fully contaminated. Accessdoors 90 provide each access to doors 88 and the downcomers. An upperportion of the downcomers may be provided with a permanent or long lifematrix such as ceramic coated, stainless steel wire mesh or the like.

The chimney portion of the exhaust system is preferably provided withfiltering means 92 of any desired type, shape and size. Also, any numberand capacity of exhaust fans such as 94 may be provided to over comeundesirable back pressure. As mentioned above, that 94 also mayrepresent power generating turbines or the like which can be used togenerate electricity by flow of the off-gas and steam down through thedowncomers. Various generating auxilliary structures such as valved,power generating gas exhaust line 86, and off-gas diverting valves 87for use when the system is generating power, may of course, be providedby those skilled in the art. In FIG. 6, the pressurized off-gas andsteam from chamber 20 flowing through grid channel 68 and treatmentsection 78 are conducted through outlets 79 to the turbine 94, as is thegas flowing down through the downcomers 70.

The preferred apparatus arrangement is shown in FIGS. 1-3 wherein theconfiguration of the off-gas flow path is circuitous, however, theapparatus shown in FIG. 4 which is essentially vertical, can findapplication for certain installation in that it allows for stacking ofchambers equivalent to 10 and 20 such that repetitive chemical scrubbingand kinetic energy reduction of the updrafted gas can be achievedwithout sacrificing significant building space such as adjoining roomsor buildings. In FIG. 4, structure equivalent to that shown in FIGS. 1-3are numbered the same.

Referring to FIG. 4, a greatly simplified, but operable, embodiment ofthe invention is shown wherein the flow path of off-gas is substantiallyvertical and in the same general direction throughout. This embodimentutilizes the kinetic energy reduction effect as does the embodiment ofFIGS. 1-3. In this embodiment the outlet 16 is defined by wall 12 and acentral conical baffle 96 supported by a spider arrangement 98. Thisbaffle assists in directing the chemically treated gases from 10 againstthe cooling coils 28 in chamber 20. Exhaust port means 22, of any numberand size, provided through the top of cylinder 23 are preferablyprovided with filter means 25 such as any of those described above.Guttering such as 100 and 102 may be provided around the inside of anyof walls 12, 18 or 32 and connected to suitable drains such as 104. Thecooling means 28 may be positioned as shown or in any other arrangementwhich is effective, and the interior 106 of cylinder 23 may be incommunication with coolant as described above. Also, the feed pipes forjets 24 and 55 may pass through cylinder 23 for pre-cooling of thechemical slurries or aqueous wash materials. The same or equivalent gasanalysis probes, analyzers, computer, reactant reservoirs, chemicalselecting means and the like described above are employed also with thisembodiment. Baffle 96 provides a convenient site for the probes 56 andanalyzer 58, however, as mentioned above, these items can be placedanywhere in the system and in any number. It is noted that the threewall sections 12, 18 and 32 are conveniently provided with bolt flangessuch as 108 such that assembly and disassembly, or repetitive stackingof sections 12 and 18 are facilitated.

Referring to FIG. 5, the variation in reactor means comprises one ormore continuous belts 82, e.g., each of a width of about two thirds thediameter of chamber 10, mounted on rollers 112 and 114, at least one ofwhich rollers is driven, and comprised of a fine mesh 116 of high heatresistant material such as stainless steel wire mesh or ceramic coatedsteel wire mesh, a reactant chemical feed plenum 118, an aqueous washdevice or plenum 120, and a catch trough 122. The top and bottom of thebelt pass through snug fitting slots 124 and 126 respectively in thechamber wall 12. The feed plenum 118 is shown as having six separatechambers for six different chemicals. Each chamber is provided with anoutlet 128 in the form of a slot or line of closely positioned aperturesrunning substantially the width of the belt. Suitable solenoid or thelike valves are provided for each outlet such that each chemical can bedispensed onto the belt selectively in accordance with the electricalsignals received from control means 30. It is preferred that the belt beprovided with a substrate material such as porous ceramic chips or thelike to which the aqueous or other chemical feeds could cling or beadsorbed, or that the feed materials themselves be in the form ofadhesive or semi-adhesive material or emulsion of innocuous chemicalcomposition such that the retention thereof by the belt is enhanced. Theporosity of the belt and any coating thereon should be sufficientlylarge to allow off-gas to readily pass therethrough and contact reactantchemical thereon. The aqueous wash device 120 having water pressureinlet 130 and wash jets 132 may be provided to remove chemicals from thebelt at the end of their life cycle. Many useful variations of suchcontinuous or semi-continuous belt type reactors will become apparent tothose skilled in the art and are within the purview of the presentinvention.

This invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications will be effected within the spirit and scope of theinvention.

I claim:
 1. An exhaust system adapted for the selective control of thetypes and concentrations of gaseous, ionic, colloidal or particulatematter emitted to the atmosphere in the off-gas of a combustion unit,said system comprising:(a) chemical treatment chamber means definedby(i) first wall means, (ii) off-gas inlet means in said first wallmeans, and (iii) outlet means in said first wall means providing exitmeans for chemically treated off-gas from said treatment chamber means;(b) second wall means defining off-gas, second chamber meanscommunicating with said outlet means of said treatment chamber means andadapted to provide a reduced pressure off-gas region; (c) exhaust portmeans in said second wall means for exiting expanded off-gas; (d)reactor means communicating with said treatment chamber means andadapted to provide reactant chemicals in contact with the off-gas insaid treatment chamber means; (e) reactant chemical selecting meansassociated with said reactor means and adapted for presenting differentchemicals and concentrations thereof to said off-gas in said treatmentchamber means; (f) cooling means for the off-gas in one or more selectedportions of said exhaust system; and (g) control means communicatingwith the off-gas at one or more locations within said exhaust system forqualitatively and quantitatively analyzing the same and actuating saidselecting means in relationship to said analysis to provide selectedreactant chemicals in predetermined quantities to said reactor means forcontact with said off-gas to selectively control the types andconcentrations of said matter therein.
 2. The system of claim 1 whereinsaid treatment chamber means is elongated and adapted for positioningabove and in communication with the fire box of a combustion unit withits longitudinal axis oriented substantially vertically.
 3. The systemof claim 1 wherein said control means provides substantially continuousoff-gas analysis and reactant chemical selection.
 4. The system of claim1 wherein said reactor means comprises multiple, pressurized fluidstreams of different chemical compositions and ejector means thereforextending into said chamber means.
 5. The system of claim 1 whereincooling means is provided for maintaining said second chamber means at areduced temperature.
 6. The system of claim 2 wherein said secondchamber means is positioned substantially vertically above saidtreatment chamber means.
 7. The system of claim 1 wherein a commoncooling means is provided for said reactor means and second chambermeans.
 8. The system of claim 7 wherein said common cooling meanscomprises heat exchanger means within said second chamber means orproximate thereto.
 9. The system of claim 1 wherein said cooling meanscomprises the cooling coils of a refrigeration unit.
 10. The system ofclaim 1 wherein said reactor means comprises variable reactant chemicalbed means.
 11. The system of claim 1 wherein slurry treatment means isprovided communicating with said second chamber means for receivingslurry therefrom, said treatment means comprising channel meanssubstantially vertically oriented and provided with baffle means forassisting in the size reduction of particulate matter during flow of theslurry downwardly in said channel means.
 12. The system of claim 11wherein said channel means substantially concentrically surrounds saidfirst wall means.
 13. The system of claim 12 wherein downcomer means isprovided communicating with said second chamber means for exhausting thetreated gasses therefrom.
 14. The system of claim 13 wherein said gassesare fed from said downcomer means to power generating, turbine means.15. The process for selectively controlling the concentration of one ormore constituents in the off-gas of a combustion unit having a fire boxand a flue system, comprising carrying out the following activities, inany order in a continuous or semi-continuous manner;(a) analyzing thechemical composition of the off-gas at one or more locations in saidflue system, (b) directing the off-gas from the fire box into chemicaltreatment chamber means maintained at predesigned off-gas pressures, (c)contacting the off-gas in said treatment chamber means with reactantchemical means previously adjusted in reactivity and specificityaccording to the chemical analysis of the off-gas, for convertingprescribed amounts of one or more of the constituents of said off-gas toone or more desired products, (d) exiting the treated off-gas from saidtreatment chamber means to second chamber means maintained atpredesigned off-gas pressures lower than the off-gas pressuresmaintained in said treatment chamber means to effect a reduction in thekinetic energy of the treated off-gas and thus facilitate removal ofparticulate matter therefrom, and (e) exiting the reduced kinetic energyoff-gas from said second chamber means to the atmosphere.
 16. Theprocess of claim 15 wherein the reduced kinetic energy off-gas is passedthrough filtering means for removing particulate matter therefrom priorto exiting to the atmosphere.
 17. The process of claim 15 wherein saidoff-gas in said second chamber means is scrubbed with aqueous materialto separate particulate matter therefrom.
 18. The process of claim 15wherein the temperature and kinetic energy of the off-gas in thetreatment chamber means is further reduced by contact of the off-gaswith heat exchanger means.
 19. The process of claim 15 wherein saidreactant chemical means comprises aqueous material containing at leastone reactant chemical and is injected as a spray into said off-gas. 20.The process of claim 19 wherein said aqueous material is injected attemperatures less than about 40 F. into said off-gas.
 21. The process ofclaim 15 wherein at least one point of analysis of the off-gascomposition is proximate the atmospheric exit of said flue system.